Endplate volumetric bone mineral density biomechanically matched interbody cage

Automatic phantom-less calibration of routine CT scans for the evaluation of osteoporosis and hip fracture risk

BACKGROUND/PURPOSE

The diagnosis of osteoporosis remains a paramount concern for orthopedic surgeons worldwide. We aim to (1) evaluate the efficacy of automatic phantom-less quantitative computed tomography (PL-QCT) in diagnosing osteoporosis and (2) investigate its clinical value in predicting hip fracture risk.

METHODS

A cohort of 705 patients was included in the study. Hip CT scans from 310 patients and spinal CT scans from 315 patients were analyzed using automatic PL-QCT. The consistency of bone mineral density (BMD) measurement obtained by dual-energy X-ray absorptiometry (DXA), phantom-based QCT (PB-QCT), and automatic PL-QCT was examined through linear regression analysis and Bland-Altman plots. The ability of automatic PL-QCT to predict osteoporosis and hip fracture risk was assessed using ROC analysis.

RESULTS

Linear regression and Bland-Altman plots demonstrated a high level of agreement between BMD measurements from PL-QCT and those from hip DXA and lumbar PB-QCT. The AUC values for PL-QCT and PB-QCT in diagnosing osteoporosis were 0.903 (95 % CI 0.852-0.955) and 0.900 (95 % CI 0.847-0.953). The AUC values for predicting hip fracture risk, based on femoral neck BMD measured by PL-QCT and DXA, were 0.869 (95 % CI 0.823-0.915) and 0.831(95 % CI 0.778-0.885), respectively. When the femoral neck BMD was combined with the percentage of inter-muscular adipose tissue area, the AUC increased to 0.929 (95 % CI 0.897-0.961).

CONCLUSION

Automatic PL-QCT has shown superior performance in predicting hip fracture risk compared to DXA. Furthermore, the novel PL-QCT demonstrates comparable predictive efficacy to that of PB-QCT, suggesting its potential as a valuable tool in clinical practice.

Improved intervertebral fusion in LLIF rabbit model with a novel titanium cage

BACKGROUND CONTEXT

There is no established small animal approach model for the strict simulation of lateral lumbar interbody fusion (LLIF) surgery.

PURPOSE

This study aims to establish a reliable LLIF rabbit model that strictly simulates the procedure and to preliminarily evaluate the differences in fusion outcomes with different graft materials.

STUDY DESIGN

A controlled laboratory.

METHODS

Fifty-four 4-month-old white New Zealand female and male rabbits were selected and divided into five groups: Group A (dissection group) consisted of 9 rabbits, Group B (normal approach group) consisted of 9 rabbits, Group C (autogenous iliac bone group) consisted of 12 rabbits, Group D (BMP-2 carrier material group) consisted of 12 rabbits, and Group E (allograft bone group) consisted of 12 rabbits. Based on data from Group A, a novel titanium metal fusion device was designed. Postoperatively, at the 12-week mark, manual palpation was employed to compare the interbody fusion status among Groups B, C, D, and E. Specimens from Groups C, D, and E were subjected to Micro-CT scanning to compare various parameters such as trabecular bone volume (BV), bone volume fraction (BV/TV, BVF), and bone surface area (BS). Furthermore, a tissue histopathological examination was performed to observe the structure and morphology of newly formed bone within the fusion mass as well as the remodeling of the graft in each group.

RESULTS

Based on the measurements obtained from the dissection group, we designed a U-shaped interbody fusion device with dimensions of 10 mm in length, 2.5 mm in width, and 1.3 mm in height. In Group B, 9 cases exhibited intervertebral mobility. In Group C, 1 case showed nonfusion. In Group D, all cases achieved fusion. In Group E, 4 cases did not achieve fusion. Additionally, the Micro-CT results showed that the interbody fusion index scores were 4.64±0.50 in Group C, 4.33±0.65 in Group D, and 3.36±0.81 in Group E. There was no statistically significant difference in fusion index scores between Groups C and D (p=.853). Notably, Groups C and D had higher scores than Group E (p<.001). The trabecular bone volume (BV) in Groups C and D also showed no significant difference but was significantly higher than in Group E (p<.001). Furthermore, the histopathological results revealed that the specimens from Group E had less newly formed cartilage and bone compared to Groups C and D.

CONCLUSIONS

This study successfully established a strict simulation of the clinical LLIF procedure in a rabbit model. Moreso, we conducted a preliminary validation indicating that the BMP-2 carrier material achieved interbody fusion outcomes similar to autogenous iliac bone.

CLINICAL SIGNIFICANCE

The findings of this investigation from animal models provide a theoretical basis for the clinical use of BMP-2 to promote early spinal fusion in LLIF procedures. Importantly, the study provides a small animal model foundation for research related to LLIF surgery.

The Role of Bone Mineral Density in a Successful Lumbar Interbody Fusion: A Narrative Review

BACKGROUND

The incidence of osteoporosis is a prime concern, especially in parts of the world where the population is aging, such as Europe or the US. Many new therapy strategies have been described to enhance bone healing. Lumbar interbody fusion (LIF) is a surgical procedure that aims to stabilize the lumbar spine by fusing two or more vertebrae using an interbody cage. LIF is a standard treatment for various spinal conditions, such as degenerative disc disease, spinal stenosis, and spondylolisthesis. However, successful fusion is challenging for patients with osteoporosis due to their reduced bone mineral density (BMD) and increased risk of cage subsidence, which can lead to implant failure and poor clinical outcomes.

METHODS

 A comprehensive literature search yielded 220 articles, with 16 ultimately included. Keywords included BMD, cage subsidence, osteoporosis, teriparatide, and lumbar interbody fusion.

RESULTS

 This review examines the relationship between BMD and LIF success, emphasizing the importance of adequate bone quality for successful fusion. Preoperative assessment methods for BMD and the impact of low BMD on fusion rates and patient outcomes are discussed. Additionally, techniques to improve fusion success in patients with weakened bone density, such as biological enhancement and BMD-matched interbody cages, are explored. However, consensus on the exact BMD threshold for a successful outcome remains elusive.

CONCLUSION

 While an apparent correlation between BMD and fusion rate in LIF procedures is acknowledged, conclusive evidence regarding the precise BMD threshold indicative of an increased risk of unfavorable outcomes remains elusive. Surgeons are advised to exercise caution in surgical planning and follow-up for patients with lower BMD. Furthermore, future research initiatives, particularly longitudinal studies, are encouraged to prioritize the examination of BMD as a fundamental risk factor, addressing gaps in the literature.